Influence of tempering methods on waxy white sorghum kernel, milling, and flour properties

Authors: YOGANANDAN, MOHANA - Kansas State University; BUENAVISTA, RANIA - Kansas State University; Bean, Scott; Aramouni, Fadi; DOGAN, HULYA - Kansas State University; SILIVERU, KALIRAMESH - Kansas State University

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2022
Publication Date: 12/1/2022
Citation: Yoganandan, M., Buenavista, R.M., Bean, S.R., Aramouni, F.M., Dogan, H., Siliveru, K. 2022. Influence of tempering methods on waxy white sorghum kernel, milling, and flour properties. Biosystems Engineering. https://doi.org/10.13031/ja.15221.
DOI: https://doi.org/10.13031/ja.15221

Interpretive Summary: Sorghum is a cereal grain commonly grown in semi-arid regions and has attracted considerable interest on the international market for its high nutritional content and gluten-free nature. Although sorghum has been a staple food crop in various regions of Asia and Africa, it remains an underutilized crop in the food industry of most developed countries where it is mostly used as animal feed. Although sorghum has many nutritional and phytochemical benefits for human consumption, the lack of functionality of sorghum flour in baked products limits its wide-spread adoption. To improve the usefulness of sorghum for baked food products, sorghum flour quality can be improved. Thus this research investigated the impact of tempering on milling and sorghum flour quality.Tempering moisture content and condition had a significant impact on waxy white sorghum kernel physical properties and flour properties. Steam tempering for 15s led to desirable physical kernel properties that would positively impact handling, transportation, and processing. In terms of milling, room temperature water tempering at 18% moisture level for 24h resulted in better bran-endosperm separation without impacting important flour quality characteristics. Room temperature water tempering at 18% w.b. for 24h is a more suitable pretreatment prior to milling of waxy white sorghum kernels in terms of flour yield and quality and can be used to improve sorghum flour for the food industry.

Technical Abstract: Purpose: To optimize yield and quality of white sorghum flour by evaluating the effects of various tempering treatments on the sorghum kernels physical properties, milling performance, and flour properties. Methods: Waxy white sorghum kernels were tempered at different moisture levels and for different times using either room temperature water, hot water, or steam. Tempered sorghum kernels were milled into flour using a milling flowsheet developed for a laboratory-scale tabletop roller mill that consists of 4 break rolls and 8 reduction rolls. Effects of these tempering methods on waxy white sorghum kernel properties, roller milling, and flour properties were investigated. Results: Tempering moisture content and condition had a significant impact on waxy white sorghum kernel physical properties and flour properties. Steam tempering for 15s led to desirable physical kernel properties that would positively impact handling, transportation, and processing: lower bulk (732.53 kg/m3), tapped (769.39 kg/m3), and true densities (1313.37 kg/m3); lower hardness index (65.01); higher abrasive hardness index (AHI) (23.73); higher angle of repose (23.60); and higher coefficients of static (0.35) and rolling friction (0.29). In terms of milling, room temperature water tempering at 18%w.b. moisture level for 24h resulted in better bran-endosperm separation without compensating important flour quality characteristics. It exhibited higher protein content (9.72%), low ash content (0.94%), high bran extraction (6.42%) and high brightness (80.67). Conclusion: Room temperature water tempering at 18% w.b. for 24h is a more suitable pretreatment prior to milling of waxy white sorghum kernels in terms of flour yield and quality.